The History of Japanese Swords
Historically, sword production falls into three broad categories:”old swords” (kotō), ”new swords” (shintō) and ”new,new swords” (shinshintō). (There are also additional subcategories that signify various differences within the different time periods.) The Battle of Sekigahara of 1600 is often cited as the borderline between "old" and "new" Japanese swords; in
other words, the type of swords made and used in Japan changed dramatically in the years surrounding the Keichō era (1596–1615). The fighting ended
with the advent of the Tokugawa Shogunate, which led to significant changes in
the demand, supply, and crafting methods for swords. While the very long tachi had been the main type of blade up through the middle of the Muromachi period (1392–1573), it was thereafter replaced with the shorter, lighter uchigatana, or katana. The change in type of of sword also influenced how they were worn. The heavier and longer tachi was worn slung from the waist, with the blade facing down. In contrast, the new katana could be worn inserted into the sash, with the blade facing up. You may notice that in photographs of Japanese swords that some are positioned with the blades facing up and others with the blades facing down. This is because tachi and katana blades are traditionally displayed in the orientation in which they would originally have been worn on the body.